Clinton: No one could have restored economy to full health in 4 years

Previewing his primetime speech tonight at the Democratic convention, former President Bill Clinton tells NBC's Brian Williams that he will explain why President Obama's economic approach "is right" and will "pay off" if he's re-elected.

Clinton also says in the interview that no president, in four years, could have restored the current economy "to full health" after the financial collapse of 2008.

Former President Bill Clinton, who will address the Democratic National Convention tonight, told NBC's Brian Williams why he feels President Obama needs to be reelected.

BRIAN WILLIAMS: Cover of Newsweek, "Why Barack needs Bill." Why do you think Barack needs Bill? What do you have to offer?

BILL CLINTON: I really don't know. I've always been mystified by that. I was honored when he asked me to nominate him. I hope what I can do, because we did have a good economy, because we did have the longest expansion in history, is explain why I think his approach is right and it'll pay off if we renew his contract. Explain why the economy he faced was much weaker and different than the one I faced, so that there's no way any president, no president could have restored it to full health in just four years.

The rest of Brian Williams' interview with Clinton will appear on NBC "Nightly News" beginning at 6:30 pm ET.